The film, with Ludivine Sagnier (left) and Rasha Bukvic, won’t be beloved.

Lung cancer, coronary thrombosis and French pop music: Two of these things will kill you, but the third will make you wish you were dead.

Dire musical interludes are sprinkled throughout the sprawling mess “Beloved,” an uninvolving would-be romantic epic that spans 45 years in the life of a mother and her daughter, starting in the early 1960s. Writer-director Christophe Honoré seems to have had in mind a sort of “Unbearable Lightness of Being” as filtered through the sensibility of Jacques Demy (who did the classic musical “The Umbrellas of Cherbourg”), but if his ambition is vast, so is his lack of talent.

The story begins in a frolicsome tone with Paris shoe-store clerk Madeleine (Ludivine Sagnier) feeling so sexy in her (stolen) pumps that she is mistaken for a streetwalker. On a lark, she agrees to a passing man’s suggestion that she have sex with him for money, a transaction she likes. She then falls in love with a subsequent customer, a visiting Czech doctor named Jaromil (Rasha Bukvic).

Jarringly, the sex farce is dropped in favor of weepy scenes in which Madeleine, who now has a young daughter, Vera, fathered by the doctor, tries to entice her now-husband to escape 1968 Prague during a Soviet invasion. In the 1970s, Madeleine is remarried in Paris. Enter the doctor, returning from Czechoslovakia to seduce her again.

All of this is broken up by unbearably bland love songs with lyrics that range from the vague and the banal to the weird and creepy: Jaromil throws Madeleine on a table in a public pool hall and practically has sex with her right there, while asking whether their daughter Vera’s breasts are as beautiful as hers.

In the 1980s, 1990s and 2000s, Honoré desperately tosses AIDS and 9/11 into the plot and brings in Catherine Deneuve and her real-life daughter (by Marcello Mastroianni) Chiara Mastroianni to play the older Madeleine and Vera, respectively, with Czech “One Flew Over the Cuckoo’s Nest” director Milos Forman now playing Jaromil.

In the latter parts of the movie, what comedy there was disappears as both Vera and Madeleine become glassy-eyed zombies who stumble randomly from one implausible situation to another.

For instance, Vera falls for a gay American drummer (Paul Schneider) who at first rejects her and then gets AIDS and becomes infatuated with her. She also has an affair with a teacher (Louis Garrel), and that he’s young enough to be her son is a fact no one seems to notice — not that the two of them seem very attached to each other to begin with. Occasionally the slow, weird story stops dead so someone can wander the lonely night singing yet another sludgy pop tune.

Struggling to achieve social significance and convey a sense of the sweep of time, Honoré forgets to give us a reason to care about any of his dull, flat characters. He has a gift for devising situations that are melodramatic without being dramatic.